The present disclosure relates generally to inkjet ink compositions.
Thermal inkjet printers use resistors to create heat, which in turn vaporizes ink to form a bubble. As the bubble expands, some of the ink is pushed out of the nozzle. A vacuum is created when the bubble collapses, which pulls more ink from the cartridge into the print head.
Inks that are predominantly water-based generally may not perform well in thermal ink jet printers. Poor performance may result because rapid water evaporation often leads to poor nozzle reliability (i.e., a crust of dried ink may clog the nozzle due to rapid water evaporation).
Predominantly non-aqueous solvent-based inks (i.e., inks made with solvents having a higher vapor pressure than water) generally have faster dry times than aqueous inks on non-absorbent substrates, due, at least in part, to higher vapor pressure and smaller latent heat of evaporation values. Non-aqueous solvent-based inks may, however, be undesirable. This may be due, at least in part, to the amount of volatile organic compounds that may be present in such inks; the potentially high volatility of such inks; and/or the potential incompatibility of such inks with adhesives and polymers. Non-aqueous solvent-based inks may also limit the materials suitable for constructing the printhead, as some of the solvents may be capable of ruining the print head.
Combination aqueous- and solvent-based inks for drop-on-demand inkjet printing generally include enough of a low vapor pressure/high boiling point solvent to assist in controlling nozzle reliability. As the water in these inks evaporates, the solvents tend to remain in the firing chamber in order to keep the colorants and other materials in the ink solubilized. However, the quantity of solvent generally used to achieve nozzle reliability may not evaporate readily, thereby increasing dry times on non-absorbent substrates.